Electronic recording material

ABSTRACT

An electronic recording material, comprising a support having a recording layer consisting of a highly insulating resin or a photoconductive layer composed of said highly insulating resin and a photoconductive substance contained therein, said resin being a resin emulsion of vinyl copolymers having a hydroxyl group and containing an acidic compound.

United States Patent Yamaguchi et al.

[111 3,793,021 1451 Feb. 19, 1974 ELECTRONIC RECORDING MATERIAL Inventors: Nario Yamaguchi; Sakae Shimizu;

Kazuo Tubuko, all of Tokyo; Kishichiro Kondo; Hiroo Iwata, both of Nagoya, all of Japan Assignees: Kabushiki Kaisha Ricoh; Ton Gosei Chemical Industry Co., Ltd., both of Tokyo, Japan Filed: Oct. 24, 1972 Appl. No.2 299,898

Related US. Application Data Division of Ser. No. 828,776, May 28-, 1969, Pat. No. 3,707,402.

1111. c1. G03g 5/00, G03g 7/00 Field 61 Search 96/l.5, 1, 1.8; 117/201; 260/80 References Cited UNITED STATES PATENTS 12/1972 Yamaguchi et al 117/201 3,138,458 6/l964 Kimble ct al. 96/1 3,48l,735 12/1969 Grayer'et al..... 96/l.5 3,306,743 2/l967 Sanders. 96/l.8 3,51 L648 S/i970 Garrett 96/l.8

Primary Examiner-Norman G. Torchin Assistant Examiner-John L. Goodrow Attorney, Agent, or Firmwoodhams, Blanchard and Flynn 8 Claims, No Drawings l ELECTRONIC RECORDING MATERIAL CROSS-REFERENCE TO RELATED APPLICATION BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to an improved electronic recording material for use in electrophotography. 2. Description of the Prior Art Electrophotographic materials include one prepared by forming a photoconductive layer consisting of a highly insulating resin containing a metallic oxide such as zinc oxide, titanium oxide and the like and one prepared by forming a recording layer consisting of a highly insulating resin only. The former is intended for developing the electrostatic latent image obtained by means of exposure through an original subsequent to impression of an electric charge by corona discharge on the photoconductive layer, while the latter is intended for developing the electrostatic latent image obtained by means of direct electrification of a recording layer like an original.

Inasmuch as the highly insulating resin to be employed for such electronic recording materials is required to function as a binder to firmly fix a photoconductive layer or a recording layer onto a support, resins having a highly insulating property and which are soluble in organic solvents have hitherto been in general use. However, the prior electronic copyingmaterials are prepared by coating the resinous binder dispersed in organic solvents on the support, so that costly equipment is necessary for preventing harm to humans and fires or explosions during vaporization of the organic solvent employed.

Viewed from the point that such precautions would not be necessary if the resinous binder is either water soluble or water dispersible, there have so far been proposed a variety of water soluble resins or water dispersible resins as the resinous binder. However, the electronic recording materials prepared by employing those resinous bindersv have such drawbacks as, the

electrostatic properties-of the photoconductive layers are deficient as evidenced by the low potential charged at the time of corona discharge and the tremendous dark decay thereof when left in a dark place subsequent to electrification, whereas when a recording layer has been provided with a latent image by direct electrification, a change in humidity is apt to give rise to fogging because of the highly insulating resin employed for said recording layer.

US. Pat. No. 3,481,735 described resinous binders for electrophotographic copying papers comprising a copolymer of hydroxy alkyl acrylate or methacrylate, copolymerizable a, ,B-un'saturated carboxylic acid and copolymerizable monoethylenically unsaturated vinyl monomers. This binder is prepared by solution polymerization and it may be applied to the support from a solvent solution thereof, or an emulsion thereof formed by emulsifying thesolution polymerized copolymer. such binders do not possess the desirable properties of higher surface potential, decreased dark decay and improved sensitivity that are obtained by our invention.

SUMMARY OF THE INVENTION The present invention provides an'improved electronic' recording material by employing polymers of vinyl emulsion having a bridge-making property in forming a photoconductive layer or a recording layer of said material.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is based on the findings resulting from examination of the electrostatic characteristics, image properties and so on of various electronic recording materials provided with a photoconductive layer or a recording layer formed on the support thereof, respectively, by means of varieties of water soluble resins and resinous emulsions obtained by emulsion polymerization. In other words, the present invention relates to a method of manufacturing an electronic recording material by means of forming on a support, such as paper and the like, a recording layer or a photoconductive layer comprising a highly insulating resin or a material composed of said highly insulating resin and a photoconductive substance contained therein, said method being characterized by the fact that the highly insulating resin employed therefor is a resin emulsion comprising vinyl copolymers having a hydroxyl group at the endof a long chain molecule or vinyl copolymers containing carboxylic acid as well as said hydroxyl group bonded at the end of along chain molecule. The electronic recording material according to the present invention has proved to be particularly superb in the weather-proofing property thereof.

It is critical that the resinous binder employed for the present invention be formed by emulsion polymerization in which the reactant monomers, catalyst, etc. are dispersed or dissolved in water. The resulting resin is obtained in the form of a latex of resin emulsified in water. The particle size of the resin is up to about 0.70p., preferably in the range of from 0.10;; to about 0.50;! The resin emulsions of vinyl copolymers, according to the present invention, are obtained by copolymerizing (I) at least one member of the group consisting of glycidyl methacrylate, glycidyl acrylate, hydroxyethyl methacrylate, 2-hydroxy-ethyl acrylate, hydroxypropyl methacrylate, hydroxy-propyl acrylate, 5-hydroxy pentylvinyl ether and the like with (11) at least one member selected from the group consisting of unsaturated monoand di-carboxylic acids such as acrylic acid, methacrylic acid, crotonic cid, itaconic acid, maleic acid, fumaric acid, and (III) at least one member selected from thegroup consisting of l) acrylic esters and methacrylic esters such as ethyl acrylate, propyl acrylate, butyl acrylate, isobutyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, pr'opyl methacrylate, butyl methacrylate, isobutyl methacrylate, hexyl methacrylate, 2- ethylhexyl methacrylate and-cyclohexyl methacrylate, (2) vinyl aromatic monomers such as styrene, a-methylstyrene, p-methylstyrene, p-methoxystyrene, vinyl toluene, vinyl xylene, isopropyl styrene, ethyl vinylbenzene and divinylbenzene, (3) ,vinyl cyanides such as acrylonitrile, methacrylonitrile and vinylidene cyanide, (4) a, B ethylenically unsaturated amides such as acrylamide, methacrylamide, N,N'-dimethylacrylamide,

. 3 N,N-dipropylmethacrylamide, N-phenylacrylamide, N-rnethylolacrylamide and N-vinylpyrrolidone, (5) vinyl amines such as 2-vinylpyridine and 3- vinylpyridine, (6) vinyl halides such as vinyl chloride, vinyl bromide, vinyl fluoride, vinylidene chloride and vinylidene fluoride, by emulsion polymerization. A substance obtained by simultaneously copolymerizing a derivative of acrylic acid having B-hydroxy radical with the foregoing monomers is applicable, and a substance obtained by mixing severally prepared emulsion polymers to form an emulsion polymer blend is also applicable.

It is also required that the resin emulsion contain at least one acidic compound having such'properties as dispersibility for zinc oxide, water resisting property of the film formed thereby and capability of enhancing the efficiency of the electronic recording materials to be produced. As acidic compounds to meet said requirements, there can be used natural resins containing resin acid, aliphatic carboxylic acids, aromatic carboxylic acids, alicyclic carboxylic acids, or substances obtained by salifying them with a volatile base. A small amount of ionic or nonionic surface active agent can be added thereto, as an optional ingredient.

The amount of acidiccompound employed in the insulating resin layer of a recording material is preferably in the range of from 1 to percent by weight, based on the total weight of theinsulating layer. The amount of the surface active agent in said insulating resin layer preferably does not exceed l percent by weight, based on the total weight of the insulating resin layer.

The amount of acidic compound employed in the photoconductive layer of an electrophotographic copying material is preferably in the range of from 0.1 to 3.0 percent, based on the total weight of the photoconductive layer. The amount of surface active agent in said photoconductive layer preferably does not exceed 0.2 percent by weight, based on the total weight of thephotoconductive layer.

The amount of photoconductive material present in the photoconductive layer can be in accordance with conventional practice and can, for example, be about 80 percent by weight of the total weight of photoconductive layer. Conventional photoconductive materials, such as zinc oxide, can be used and conventional sensitizers can be used,if desired. Our invention is not concerned with any discovery relating to photoconductive materials and any suitable conventional can be followed with regard to them.

As for said natural resin containing resin acid, it includes elemi, gurjun, jalap, scammonium, bdellium, sagapenum, Euphorbium, myrrh, Opopanax, guajak, takamahak, galbanum, gamboge, olibanum, ammoniacum, asafetida, benzoin, sandarak, kawa kawa, a

'variety of balsams such as canada balsam, mecca balsam, true balsam, copaiba balsam and peru balsam, a variety of dammars such as .benak, dead dammar, me-

practices lanty, chan, yan, panoun, and papuan dammar, a vari ety of kopals such as kauri kopal, soft manila kopal,

hard manila kopal, congo kopal, benguela kopal, ann gora kopal, demera kopal, madagaskar kopal, hard bornea kopal and new zealand hard kopal, a variety of the general formula C,,H ,COOH and having five or more carbons, such as valeric acid, isovaleric acid, caproic acid, enanthic acid, pelargonic acid, caprylic acid, undecanoic acid, lauric acid and tridecanoic acid, the group of olefin monocarboxylic acids expressed by the general formula C,,H COOH and having five or more carbons, such as angelica acid, tiglic acid, 1- pentenoic acid, 2-hexenoic acid, Z-heptenoic acid, 2- octenoic acid, 2-nonenoic acid, 4-decenoic acid, linderic acid, elaidic acid and oleic acid, the group of acetylene monocarboxylic acids expressed by the general formula C H C C(CH ),,,COOH and having five or more carbons, such as ethylpropiolic acid, npropylpropiolic acid and beh'enolic acid, the group of diand tri-olefin monocarboxylic acids expressed by the general formulas C l-l COOH or C,,H COOH and having 5 or more carbons, such as 2,4- pentadienoic acid, 2,4-hexadienoic acid, linolic acid, elaeostearic acid, and linolenic acid, the group of saturated dicarboxylic acids expressed by the general formula HOOC(CH ),,COOR (wherein R is hydrogen or an alkyl radical) and having 4 or more carbons, such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid and sebacic acid as well as monoesters of these acids, and also the group of hydroxycarboxylic acids having five or more carbons, such as 2-hydroxyvaleric acid, 2-hydroxycaproic acid, 2-hydroxyenanthic acid, 2-hydroxycaprylic acid, 3- hydroxycaprylic acid and 3-hydroxyundecanoic acid.

As for said aromatic carboxylic acid and alicyclic carboxylic acid, the former includes the group of benzoic acids such as toluylic acid, dimethyl benzoic acid and ethylbenzoic acid, the group of benzenedicarboxylic acids such as o-phthalic acid, m-phthalic acid and terephthalic acid, the group of benzenetricarboxylic acids such as hemimellitic acid, trimellitic acid and trimesic acid, the group of sulfocarboxylic acids such as ortho-sulfocarboxylic acid, metasulfocarboxylic acid and para-sulfocarboxylic acid, the group of alkylbenzene-sulfocarboxylic acids such as 2- methylbenzenesulfocarboxylic acid and 2- and 6- dimethylbenzenesulfocarboxylic acid, the group of hydroxycarboxylic acids such as hydroxybenzoic acid, methyl-salicyclic acid and 3-hydroxy-phthalic acid, the group of anthracenecarboxylic acids such as naphthoic acid, Z-methyl-l-naphthoic acid, 3-hydroxy-2- naphthoic acid and naphthalene-l,Z-dicarboxylic acid, and further anthracene-l-carboxylic acid and anthracenel,2-dicarboxylic acid, while the latter viz. alicyclic carboxylic acid includes the group of cyclopropane-carboxylic acids such as 3-ahydroxybenzyl-2-phenylcyclopropane-carboxylic acid, 3-benzoyl-2-phenylcyclopropanecarboxylic acid and dicyclopropane-l,l-dicarboxylic acid, the group of cyclobutanecarboxylic acids such as cyclobutanecarboxylic acid, 2-methylcyclobutanecarboxylic acid and cyclobutane-l,l-di-carboxylic acid, the groupof cyclopentanecarboxylic acids such as methylcyclopentanecarboxylic acid, .l-isopropylether-2-methycy- *clopentanecarboxylic acid, 1- and 2-cyclopentanerosin such as gum rosin, heterogeneous rosin, polymerized rosin, hydrogenated rosin, tall oil, rosin maleate, rosin oxide, hardened rosin and ester gum.

As for said aliphatic carboxylic acid, it includes the group of saturated monocarboxylic acids expressed by dicarboxylic acid, cyclopentane acetic acid, naphthenic acid and l-hydroxypentanecarboxylic acid, the group of cyclohexane-carboxylic acids such as methylcyclohexanecarboxylic acid, cyclohexylpropanecarboxylic acid, l-phenylcyclohexyl acetate and cyclohexenecarboxylic acid, the group of terpenes such as abietic acid, B-boswelic acid, quinovic acid,

glycylrhezio acid, hederagenin oleanolic acid, pimaric acid, quillaic acid and ursolic acid, and the group of cholic acids such as bisnorchonic acid, chenodesoxycholic acid, cholanic acid, dehydrocholic acid, glycocholic acid, hidesoxycoalic acid, lithocholic acid and ursodioxycholic acid.

As for the aforesaid surface active agent to be employed in combination with the foregoing acids or such substances as obtained by neutralizing said acids with a volatile base, it includes, for example, sodium stearate, potassium laurate, sodium laurate, 2-ethylhexylsodiumsulfate, triethylamine xylenesulfonate, diethylamine xylenesulfonate, triethanolamine alkylbenzenesulfonate, diethylamine alkylbenzenesulfonate and triethylamine alkylbenzenesulfonate.

The vinyl polymer latex obtained through an ordinary emulsion polymerization by employing the abovestated monomer composition and emulsifier has a pH value in the range of 1.5 3.5, but, due to neutralization by means of a volatile alkaline aqueous solution such as ammonia, morpholine, cyclohexylamine, an aliphatic primary amine, e.g. methylamine, ethylamine, and isopropylamine, an aliphatic secondary amine, e.g. dimethylamine, diethylamine and dipropylamine, an aliphatic tertiary amine, e.g. trimethylamine, triethylamine and tri-isopropylamine, and alcoholamines, e.g. monoethanolamine, diethanolamine and triethanolamine, the acidic component 'of the emulsifier as well as the acidic component of a copolymer latex as stated above is neutralized by virtue of said volatile base, and, as a result, a superb preservation stability and mechanical stability is obtained, the pigment dispersion effect is extremely improved, as has been confirmed by experiment.

The volatile base is easily evaporated by heating in air at the time of forming the film. The aforesaid polymer latex contains a small amount or none of an intensively hydrophilic surface active agent and has excellent water-resisting qualities ascribable to a multiplied effect of the natural resin acid, fatty acid, aromatic alicyclic carboxylic acid, etc. having a large number of carbons, and especially has such an advantage that it can provide a film possessing a superb electric insulating property which is hardlyinfluenced by humidity.

Moreover, said resin emulsion, when employed as a binder to be dispersed in water together with a photoconductive substance and a sensitizer, exhibits an excellent dispersion effect, and, not only that, a sensitive layer formed by coating the resultant dispersion on the surface of a support and drying thereafter, can be provided with another excellent character. That is to say, the epoxide radical or hydroxyl group contained in the resinous binder causes a bridge-making reaction with the acidic component of the copolymer or the carboxylic acid contained in the emulsifier during the hot drying process at the timeof forming the sensitive layer and easily forms reticulations among molecules or within molecules, to thereby bring about a superb weather-proofing property. For instance, a recording material according to the present invention can display such properties and the copied images are by no means inferior to those obtained in an atmosphere of high humidity. This is presumably attributable to the fact that, owing to the reticulations of the resinous binder formed within the sensitive layer, it becomes difficult for the photocondctive substance to absorb the moisture of the atmosphere.

As mentioned above, the present invention relates to an electronic recording material comprising a support and a photoconductive layer or a recording layer formed on the surface of said support, and has been successful particularly in effecting a novel improvement of the above stated binders to thereby provide a sensitive layer with weather-proofing qualities so as to enhance the non-susceptibility of the electric resistance of said sensitive layer to the humidity of the atmosphere as required for an electrophotograph, and also in eliminating all such defects as are attributable to those binders which are dissolved in organic solvents only, as in case of the electronic recording materials in the prior art.

The following is a further elucidation of the present invention with reference to specific embodiments thereof.

EXAMPLE 1 (A-RESIN EMULSION) As-the resin material in this example, 60 parts by weight of methyl acrylate, 20 parts by weight of ethyl acrylate, 15 parts by weight of glycidyl methacrylate, 5 parts by weight of acrylic acid, 4 parts by weight of dammar, 0.1 part by weight of triethanolamine dodecylbenzenesulfonate, 0.3 part by weight of ammonium persulfate and 150 parts by weight of water were employed. A two-liter glass flask equipped with a stirrer, a counterflow cooler, a raw material inlet and a thermometer, was installed in a hot-water bath, and into this flask were placed said monomers, dammar, dodecylbenzenesulfonate and water (exclusive of the quantity used for dissolving the ammonium persulfate). Then, nitrogen gas was introduced into the flask to replace the air therein, and the inner temperature of the flask was raised to 65 C. by slowly raising the temperature of the hot-water bath. The ammonium persulfate was divided into three doses, and the doses were introduced into the flask at intervals of 1 hour so as to control the temperature of the reaction. The material thus mixed was subjected to a further intense stirring continuously for some time, and a resinous emulsion having 39.7% of solid matter and a pH value of 2.8 was obtained after polymerization for 6 hours in all.

(B-RESIN EMULSION) COMPARATIVE Another resin emulsion was prepared in the same way as the foregoing A resin emulsion, except that glycidyl methacrylate was omitted from the monomer components of the emulsion. By employing 50g. of the thus obtained resinous emulsions and adding thereto, respectively, 100g. of photoconductive zinc oxide, 100g. of water and Sec of sensitizing dye (viz. a methanol solution containing 1% of Bromophenol Blue, 0.5% of Fluorescein and 0.1% of Rose Bengal), and further adding a small amount of aqueous ammonia and dispersing the resultant mixture with a homomixer, electrophotographic sensitive liquids were prepared. Then, said sensitive liquids were respectively coated on the surfaces of an art paper, whose back had been processed for conductivity, to the extent that the weight of the sensitive layer, when dried, was 25g/m and was dried. The thus obtained copying paper was measured as to its electric charge by means of corona discharge according to the conventional method under high temperature and humidity of 32 C and RH, respectively. The resultant surface electric potential (as ex- TABLE 1 Copying paper Product A of this invention Product B for comparisons sake Vs/u (32C 85% RH) 59 volts 20 volts Further, when development was effected by means of a wet-developing process or a dry-developing process subsequent to impression of an electric charge and exposure according to the conventional method, product A of the present invention brought about an image of good contrast if it was under high temperature and humidity or under normal temperature, whereas product B prepared for comparisons sake hardly exhibited any image-formability.

EXAMPLE 2 (C-RESIN EMULSION) As the resin material in this Example, 50 parts by weight of styrene, 30 parts by weight of methyl methacrylate, 18 parts by weight of hydroxypropylacrylate, 2 parts by weight of acrylic acid, -3 parts by weight of kauri kopal, 0.01 part by weight of dialkylsulfosuccinate, 0.2 part by weight of ammonium persulfate and 150 parts by weight of water were employed. Kauri kopal was first thoroughlydissolved in the monomers, and then all the materials were put in the flask as in the foregoing Example I to effect 7 hours polymerization under the reaction temperature of 70 C. The resultant resin emlusion contained 40% of solid matter and had a pH value of 2.6.

(D-RESIN EMULSION) COMPARATIVE TABLE 2 Copying paper Vs/p. 32C 80% Vs/p. (25C 50% RH) Product of this 63 volts 65 volts invention Product D for 18 volts 3l volts comparison 5 sake Further, when development was effected by means of a wet-developing-type electrophotographic copying press, product C of the present invention formed images of superior quality under normal temperature and humidity or under high temperature and humidity, whereas product D prepared for comparisons sake exhibited an image of inferior contrast.

EXAMPLE 3 (E-RESIN EMULSION) In this Example, by employing 45 parts by weight of ethyl acrylate, 30 parts by weight of acrylonitrile, parts by weight of 2-hydroxyethylacrylate, 2 parts by 8 weight of acrylic acid, 13 parts by weight of abietic acid, 0.09 part by weight of dodecylbenzenesulfonic acid, 0.2 part by weight of ammonium persulfate, I50 parts by weight of water and Sec of triethylamine, said abietic acid was salified. Then, all the materials were placed in a flask for 5 hours polymerization at a temperature of C. The resultant resin emulsion contained 40.5% of solid matter and had a pH value of 8.5.

(F-RESIN EMULSION) COMPARATIVE This F-resin emulsion was prepared by means of emulsion polymerization of the same material as that of the foregoing E-resin emulsion except that 2-hydroxyethylacrylate and abietic acid were omitted from the monomers for the present emulsion. Subsequently, for the sake of comparison, a layer of each of the respective resins weighing log/m when dried, was formed on the surface of an art paper, whose back had been processed for conductivity, by coating the resin emlusion alone with a rotary coating apparatus. The thus obtained resin layer was measured as regards its electrification property in the same way as in case of the copying paper of Example l,'under 32 C and RH. As a result, the electric charge ofthe insulating layer of the E-resin emulsion according to the present invention was 68 (V) (Vs/u), while the F-resin emulsion prepared for use for comparison was 26 (V) (VS/u). When these emulsions were respectively employed for preparing an electrostatic recording paper, the insulating layer of the E-resin emulsion according to the present invention exhibited a marvelous image-formability even under a high temperature and humidity, whereas the F-resin emulsion produced an image of low concentration.

EXAMPLE 4 (G-RESIN EMULSION) The material comprising 50 parts by weight of styrene, 45 parts by weight of butyl acrylate, 5 parts by weight of acrylic acid, 4 parts by weight of oleic acid, 0.3 part by weight of diethylaminedodecylbenzenesulfonate, 0.2 part by weight of ammonium persulfate and parts by weight of water was put in the flask for 5 hours polymerization at a temperature of 63 C. The resultant resin emulsion contained 41.3% of solid matter, and had a pH value of 2.6.

(I-I-RESIN EMULSION) A material comprising 50 parts by weight of styrene, 40 parts by weight of butyl acrylate, 10 parts by weight of glycidyl methacrylate, 4 parts by weight of ammonium oleate, 0.2 part by weight of ammonium persulfate and 150 parts by weight of water was put in a flask for 4 hours polymerization at a temperature of 68 C. The resultant resin emulsion contained 40% of solid matter, and had a pH value of 7.7.

(I-RESIN EMULSION)- COMPARATIVE Another resin emulsion was prepared by polymerization in the same way as the foregoing I-I-resin emulsion except that glycidyl methacrylate was omitted from the monomer components of this emulsion.

A copying paper prepared by applying a blended emulsion comprising the foregoing G-resin emulsion and H-resin emulsion according to the present invention mixed at the weight ratio of 1:1 produced a clearcut image even under a high temperature and humidity, whereas a copying paper prepared by applying a blended emulsion comprising said G-resin emulsion and I-resin emulsion, which was intended for use in comparison, mixed at the weight ratio of 1:1 had a very poor image-formability under a high humidity.

EXAMPLE (L-RESIN EMULSION) A material comprising 20 parts by weight of 2- ethylhexyl acrylate, 65 parts by weight of styrene, parts by weight of methyl methacrylate, 6 parts by weight of glycidyl methacrylate, 1 part by weight of acrylic acid, 3 parts by weight of phthalic acid, 0.5 part by weight of triethanolamine palmitate, 0.2 part by weight of ammonium persulfate and 150 parts by weight of water was put in the flask for 5 hours polymerization at a temperature of 70 C. The resultant resin emulsion contained 40.5% of solid matter, and had a pH value of 4.0.

(M-RESIN EMULSION) COMPARATIVE This resin emulsion was prepared by polymerization in the same way as the L-resin emulsion above except that glycidyl methacrylate was omitted from the monomer components of this emulsion.

(N-RESIN EMULSION) COMPARATIVE This emulsion was prepared by polymerization in the same way as the foregoing L-resin emulsion except that phthalic acid was omitted from the monomer components of this emulsion. For the sake of comparing said L, M and N resin emulsions with one another, copying papers were respectively prepared by applying each of those electrophotographic sensitive liquids which were prepared by employing said resin emulsions respectively in accordance with Example 1. The property of each copying paper thus prepared was as shown in the following Table 3. It is evident that the impression of voltage on the copying paper according to the present invention is excellent.

TABLE 3 Copying paper Vs/p. (32C 90% RH) emulsion for comparisons sake EXAMPLE 6 Preparations and tests were carried out as follows:

SAMPLE (A) (CONTROL) A mixture of 177.6 g of methyl methacrylate, 201.6 g of styrene, 272.4 of butyl methacrylate, 272.4 g of butyl acrylate, 97.2 g of acrylic acid, and 147.5 g of a 96% solution of hydroxypropyl methacrylate in xylene (which also contained 4.8 g of methacrylic acid), 24 g of azo-bis-isobutyronitrile and 12 g of di-tertiarylbutyl peroxide was added to 340 g of ethyl Cellosolve in an autoclave. The monomer-catalyst mixture was added over a 2-hour period to the autoclave which was maintained at a temperature of 345 350 F. The pressure increased to 100 p.s.i.g. during the addition. Additional solvent (122 g) was added to obtain a 70% nonvolatiles solution. A booster catalyst of 3.5 g of ditertiarybutyl peroxide was added four hours after the monomer addition was completed. The total reaction time (including monomer addition) was ten hours. The copolymer had a final viscosity of 14 stokes at 70.2% NV. The acid value of the solution was 45.6. An 800 g portion of this copolymeric solution was mixed with 239 g of ethyl Cellosolve, 41.5 g of triethyl amine, and 280.5 g of water to obtain a copolymer dispersion. Next, 38.2 g of the copolymer dispersion were mixed with zinc oxide and sensitizing dyes (5 cc of methanol solutions of 1% of Bromophenol Blue, 0.5% of fluorescein, and 0.1% of Rose Bengal). The weight ratio of zinc oxide to copolymer was about 5:1. The resulting composition was then applied to electroconductive paper to obtain a dry coating weight of 25 g/m Sample (B) A sample prepared according to the present invention using the same monomers and amounts thereof as in Sample (A).

A solution prepared by dissolving 5 g of sodium dodecyl-benzene sulfonate into 1,800 g of water and adding 5 g of ammonium persulfate (polymerization initiator) to the resulting aqueous solution was put in a three-necked flask and maintained at a temperature of C. Into this solution was slowly dropped a mixture of monomers and naphthenic acid having the following composition.

methyl methacrylate 177.6 g styrene 201.6 g butyl methacrylate 272.4 g butyl acrylate 272.4 g acrylic acid 97.2 g hydroxypropyl methacrylate 147.5 g naphthenie acid 33.4 g

By effecting polymerization at 70 C for 7 hours following the completion of the addition of the mixture, a resin emulsion having 40.0 wt. of solid matter and a pH of 2.4 was obtained.

Next, a photoconductive-layer forming dispersion was prepared by mixing together g of zinc oxide, 50 g of the foregoing emulsion, 5 cc of sensitizing dyes (a methanol solution of 1% Bromophenol Blue, 0.5% of fluorescein, and 0.1% of Rose Bengal), 100 g of water and 1 cc of triethyl amine. The ratio of zinc oxide to copolymer was about 5:1. This dispersion was applied to the same electroconductive paper as that used in the foregoing Sample (A) so as to obtain a dry coating weight of 25 g/m and was then dried to obtain an electrophotographic copying material.

SAMPLE (C) By carrying out the same process as in the foregoing (B), except that palmitic acid was substituted for naphthenic acid, an electrophotographic copying material was obtained.

SAMPLE (D) By carrying out the same process as that in (B) above, except that abietic acid was substituted for naphthenic acid, an electrophotographic copying material was obtained.

SAMPLE (E) SAMPLEE (F) By carrying out the same process as that in (B) above, except that kauri kopal was substituted for naphthenic acid, an electrophotographic copying mate rial was obtained.

SAMPLE (G) Another sample according to the present invention, but employing a different monomer composition.

Fifty (50) parts by weight of styrene, 30 parts by weight of methyl methacrylate, 18 parts by weight of hydroxypropyl acrylate, 2 parts by weight of acrylic acid, 3 parts by weight of kauri kopal, 001- part by weight of dialkylsulfosuccinate, 0.2 part by weight of ammonium persulfate and 150 parts by weight of water were employed. A two-liter glass flask equipped with a stirrer, a counterflow cooler, a raw material inlet and a thermometer, was installed in a hot-water bath, and into this flask were placed said monomers, kauri kopal, dialkyl-sulfosuccinate and water (exclusive of the quantity used for dissolving the ammonium persulfate). Then, nitrogen gas was introduced into the flask to replace the air therein, and the temperature of the contents of the flask was raised to 65-70 C by slowly raising the temperature of the hot-water bath. Ammonium persulfate was divided into three doses, and the doses were introduced into the flask at intervals of one hour so as to'control the temperature of the reaction. The material thus mixed was subjected to a further intense stirring continuously for some time, and a resinous emulsion having 40 wt. of solid matter and a pH of 2.6 was obtained after a total polymerization time of 7 hours. By employing 50 g of the thus obtained resinous aqueous emulsion and adding thereto 100 g of photoconductive zinc oxide, 100 g of water and cc of sensitizing dyes (viz. a methanol solution containing 1% of Bromophenol Blue, 0.5% of fluorescein and 0.1% of Rose Bengal), and further adding a small amount of aqueous ammonia and dispersing the resultant mixture with a homomixer, an electrophotographic sensitive liquid was obtained. Then, said liquid was coated on the surface of an art paper, whose back had been processed for conductivity, inan amount such that the dry weight of the resulting photosensitive layer was g/m Sample (H) (Control) A sample prepared employing the same monomers as in (G) above and prepared by solution polymerization and subsequent emulsification of the polymer.

styrene methyl methacrylate hydroxypropyl acrylate acrylic acid azobis-isobutyronitrile toluene 50 parts by weight parts by weight 18 parts by weight 2 parts by weight 09 part by weight 75 parts by weight l2 triethyl amine were put in a 300 cc beaker and dispersedwith a homomixer, whereby an emulsion containing 40 wt. of solid matters was obtained.

Subsequently, a photoconductive-layer forming dis- I persion was prepared by mixing 50 g of this emulsion, 100 g of zinc oxide,l00 g of water, and 5 cc of sensitizing dyes (a methanol solution containing 1% of Bromophenol Blue, 0.5% of fluorescein and 0.1% of Rose Bengal). By applying this dispersion to the same support as employed in (G) above, so as to obtain a dry coating weight of 25 g/m, an electrophotographic copying material was obtained.

SAMPLE (1) Another sample prepared according to the present invention using a different monomer composition.

In this case, there was employed 45 parts by weight of ethyl acrylate, 30 parts by weight of acrylonitrile, 10 parts by weight of 2-hydroxyethylacrylate, 2 parts by weight of acrylic acid, 13 parts by weight of abietic acid salified with 5 cc of triethylamine, 0.09 part by weight of dodecylbenzenesulfonic acid, 0.2 part by weight of ammonium persulfate, and 150 parts by weight of water. Then, the materials were placed in a flask for 5 hours polymerization at a temperature of C. The resultant resin emulsion contained 40.5 wt. of solid matter and had a pH of 8.5. By employing this resin emulsion and applying the same process as in (G), an electrophotographic copying material was obtained. Sample (J) (Control) A sample prepared by employing the same monomers as in Sample (I) above and prepared by solution polymerization followed by subsequent emulsification offthe polymer.

carrying out the same process as in the foregoing (H),

an electrophotographic copying material was obtained.

Tests for measuring the electrostatic properties of Samples (A) (J) a. A negative charge was impressed on each of Samples (A) (J) for 30 seconds under the conditions of 25 C and 63% RH by the use of a 6.2 kv corona discharge, and the surface potentials (V,,) of said samples (A) (J) were measured. After the said samples were allowed to stand in a dark place for 30 seconds after stopping the corona discharge, measurements of the surface potential (V,,) were also carried out with respect to each of the aforesaid samples in order to calculate V, V /V, X dark decay. Exposure to each Sample (A) (J) was then effected, following the measurement of the V value, and the number of lux. Seconds required until the surface potential was reduced to zero was measured. A potentiometer manufactured by RlON Co. was used for measuring the above surface potentials.

In addition, the time required until the surface potential reached V, was measured to calculate the buildingup velocity (V/sec).

b. The dispersed resin particles in each water emulsified resinous binder made in the preparation of aforesaid samples (A) (J) were observed by the use of an electron microscope to measure the particle size.

RESULTS V, (Volt) Dark decay Sensitivity (lux. sec) Building-up velocity Resinous purticlc size (n) (V/sec) (A) control 364 10.8 335 50 0.80-2.50 (B) 438 3.0 2l0 63 0.l-0.30 (C) 420 2.5 224 58 0.13-0.38 (D) 465 2.5 238 63 0.20-0.43 (E) 430 3.0 206 62 0.10-0.25 (F) 418 3.5 2l0 54 0.10-0.30 (G) 419 3.0 245 58 0.10-0.30

(H control 360 7.8 SM .52 0.70-3.00 (l) 417 2.2 231 64 0.l0-0.35

(.I) control 324 8.4 295 55 0.80-3.00

The electrophotographic copying materials Samples (B) (G) and (I) prepared by the method of the present invention are superior to the electrophotographic copying materials Samples (A), (H) and (J) especially in the properties of higher surface potential (V,), decreased dark decay and sensitivity. It should be noted that a lower value of sensitivity (lux. sec.) is better because it indicates that exposure can be carried out more rapidly. The results thus show that an insulating layer made of an emulsion polymerized resinous emulsion containing an acidic compound is greatly superior to an insulating layer made by solution polymerization and subsequent water emulsification and not containing an acidic compound.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: V V

l. A dielectric recording material comprising a support having an insulating layer on one surface thereof,

said insulating layer consisting essentially of a mixture of A. a copolymer of l. at least one monomer selected from the group consisting of glycidyl methacrylate, glycidyl acrylate, hydroxyethyl methacrylate, Z-hydroxyethylacrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate and S-hydroxy pentyl-vinyl ether, t

2. at least one monomer selected from the group consisting of acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid and fumaric acid,

3. at least one monomer selected from the group consisting of acrylic esters, methacrylic esters, vinyl aromatic monomers, vinyl cyanides, a, Bethylenically unsaturated amides, vinyl amines andvinyl halides, and

r B. at least one acidic compound dispersed in said copolymer and selected from the group consisting of aliphatic carboxylic acids, aromatic carboxylic acids, alicyclic carboxylic acids and natural resins containing resin acid.

2. A dielectric recording material according to claim 1, in which said insulating layer further contains a surface active agent selected from the group consisting of sodium stearate, potassium laurate, sodium laurate, 2-ethylhexylsodiumsulfate, triethylamine xylenesulfonate, diethylamine xylenesulfonate, triethanolamine alkylbenzenesulfonate, diethylamine alkylbenzenesulfonate, triethylamine alkylbenzenesulfonate, dialkylsulfo-succinate, dodecylbenzene sulfonic acid, triethanolamine palmitate and ammonium dodecylbenzene sulfonate.

3. A dielectric recording material according to claim 1, in which the total amount of ingredient (B) is from 1 to 15 percent by weight, based on the total weight of the insulating layer.

4. A dielectric recording material according to claim 2, in which the total amountof the surface active agent is less than 1 percent by weight, based on the total weight of the insulating layer.

5. An electrophotographic copying material comprising an electroconductive support having on one surface thereof a photoconductive layer consisting essentially of A. a copolymer of r l. at least one monomer selected from the group consisting of glycidyl methacrylate, glycidyl acrylate, hydroxyethyl, methacrylate, 2-hydroxyethylacrylate, hydroxypropyl methacrylate, hydroxypropyl acrylateand 5-hydroxy pentylvinyl ether,

2. at least one monomer selected from the group consisting of acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid and fumaric acid,

3. at least one monomer selected from the group consisting of acrylic esters, methacrylic esters, vinyl aromatic monomers, vinyl cyanides, a, Bethylenically unsaturated amides, vinyl amines and vinyl halides, and

B. at least one acidic compound dispersed in said binder and selected from the group consisting of aliphatic carboxylic acids, aromatic carboxylic acids, alicyclic carboxylic acids and natural resins containing resin acid C. an inorganic photoconductive substance dispersed in said resinous binder.

6. An electrophotographic copying material according to claim 5, in which said photoconductive layer further contains dispersed therein a surface active agent selected from the group consisting of sodium stearate, potassium laurate, sodiumlaurate, 2-ethyl-hexylsodiumsulfate, triethylamine xylenesulfonate, diethylamine xylenesulfonate, triethanolamine alkylbenzenesulfonate, diethylamine alkylbenzenesulfonate, triethylamine alkylbenzenesulfonate, dialkylsulfosuccinate dodecylbenzene sulfonic acid, triethanolamine palmitate and ammonium dodecylbenzene sulfonate.

7. An electrophotographic copying material according to claim 5, in which the total amount of ingredient (B) is from 0.1 to 3.0 percent by weight, based on the total weight of the photoconductive layer.

8. An electrophotographic copying material according to claim 6, in which the total amount of the surface active agent is less than 0.2 percent by weight, based on the total weight of the photoconductive layer.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Piatent No. 3 793 021 Dated February 19, 1974 Nario Yamaguchi, Sakae Shimizu, Kazuo Tubuko,

Invmnmr(s) Kishichiro Kondo and Hiroo Iwata It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the heading, please insert the following:

+Priority: June 8, 1968 Japan..... 39 348-.

Signed and sealed this 30th day of July 1974.

(SEAL) Attest:

MCCOY M. GIBSON, JR. 0. MARSHALL DANN Attesting Officer Commissioner of Patents USCOMM- D'C 60376-P69 FORM l e-1050 (10-69) U.S. GOVERNMENT 'RI'ITING OFFICE I ll, 0Ji6-JJ|. 

2. at least one monomer selected from the group consisting of acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid and fumaric acid,
 2. at least one monomer selected from the group consisting of acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid and fumaric acid,
 2. A dielectric recording material according to claim 1, in which said insulating layer further contains a surface active agent selected from the group consisting of sodium stearate, potassium laurate, sodium laurate, 2-ethylhexylsodiumsulFate, triethylamine xylenesulfonate, diethylamine xylenesulfonate, triethanolamine alkylbenzenesulfonate, diethylamine alkylbenzene-sulfonate, triethylamine alkylbenzenesulfonate, dialkylsulfo-succinate, dodecylbenzene sulfonic acid, triethanolamine palmitate and ammonium dodecylbenzene sulfonate.
 3. at least one monomer selected from the group consisting of acrylic esters, methacrylic esters, vinyl aromatic monomers, vinyl cyanides, Alpha , Beta ethylenically unsaturated amides, vinyl amines and vinyl halides, and B. at least one acidic compound dispersed in said copolymer and selected from the group consisting of aliphatic carboxylic acids, aromatic carboxylic acids, alicyclic carboxylic acids and natural resins containing resin acid.
 3. A dielectric recording material according to claim 1, in which the total amount of ingredient (B) is from 1 to 15 percent by weight, based on the total weight of the insulating layer.
 3. at least one monomer selected from the group consisting of acrylic esters, methacrylic esters, vinyl aromatic monomers, vinyl cyanides, Alpha , Beta ethylenically unsaturated amides, vinyl amines and vinyl halides, and B. at least one acidic compound dispersed in said binder and selected from the group consisting of aliphatic carboxylic acids, aromatic carboxylic acids, alicyclic carboxylic acids and natural resins containing resin acid C. an inorganic photoconductive substance dispersed in said resinous binder.
 4. A dielectric recording material according to claim 2, in which the total amount of the surface active agent is less than 1 percent by weight, based on the total weight of the insulating layer.
 5. An electrophotographic copying material comprising an electroconductive support having on one surface thereof a photoconductive layer consisting essentially of A. a copolymer of
 6. An electrophotographic copying material according to claim 5, in which said photoconductive layer further contains dispersed therein a surface active agent selected from the group consisting of sodium stearate, potassium laurate, sodium laurate, 2-ethyl-hexylsodiumsulfate, triethylamine xylenesulfonate, diethylamine xylenesulfonate, triethanolamine alkylbenzenesulfonate, diethylamine alkylbenzenesulfonate, triethylamine alkylbenzenesulfonate, dialkylsulfosuccinate dodecylbenzene sulfonic acid, triethanolamine palmitate and ammonium dodecylbenzene sulfonate.
 7. An electrophotographic copying material according to claim 5, in which the total amount of ingredient (B) is from 0.1 to 3.0 percent by weight, based on the total weight of the photoconductive layer.
 8. An electrophotographic copying material according to claim 6, in which the total amount of the surface active agent is less than 0.2 percent by weight, based on the total weight of the photoconductive layer. 